Increasing the life span of cheese

Natural, edible coatings with an antimicrobial capacity have been found to increase the shelf life of soft cheeses.

Researchers at the Universitat Politècnica de València (UPV) have incorporated oregano and rosemary essential oils along with chitosan, a by-product that comes from crustacean shells, into a totally edible film which they claim increases the life span of soft cheese.

Chelo González, a researcher at the Institute of Food Engineering for Development of the UPV, explained that, “The most common causes of deterioration are excessive surface dehydration and the growth of microorganisms such as fungus or yeasts, which produce a strange flavour or odour, a slimy texture and a significant visual alteration.”

Today, the most widely used method of avoiding fungal growth in cheese is the application of natamycin (or pimaricin) - a common antifungal polyene macrolide that binds specifically to ergosterol and blocks fungal growth - and a coating of polyvinyl acetate plastic. Currently the life span of commercial soft cheese treated with pimaricin is about 21 days in cold storage.

However, the edible coating developed by the UPV researchers now offers processors a natural alternative to the pimaricin and polyvinyl combination that is commonly used on commercial cheeses.

“The product that we have obtained is an alternative to the use of pimaricin and non-edible plastics. Moreover, using a natural and edible product reduces the fungal problems and controls the weight loss during the maturing,” said González.

Another possible application for the antimicrobial film is in mature cheese where it can be used to decrease the growth of fungus on the surface of the cheese during the maturing process. If these cheeses have pressing faults or fissures the surface fungus can enter into the pieces and significantly reduce their value. “In this case, applying the coatings that we have developed will reduce the proportion of product losses in the cheese factories and therefore the important economic losses that this implies,” explained González.

Of the oils used, the oregano oil was the most effective, inhibiting the fungal growth in a similar way to a conventional pimaricin treatment. Moreover, the researchers conducted a sensory study that enabled them to adjust the concentration of the essential oil in order to obtain formulations with antifungal activity together with good sensory acceptance. In fact, the more than 100 panellists that were used for the sensorial analysis gave higher scores for the cheese coated with essential oils, for taste and odour attributes, in comparison with the uncoated cheese.

Researchers at the Institute for Animal Science and Technology, led by Professor Pilar Molina, and at the Department of Agroforest Ecosystems of the UPV, led by Pilar Santamarina, have also participated in this project. The conclusions of this work were presented in the last edition of the Iberoamerican Congress in Food Engineering and they will be released shortly in the International Journal of Food Studies